Questions tagged [rf]
Short for Radio-Frequency. Frequencies at which radiation (intentional or not) plays a role. Typically associated with wireless communications, but also relevant for high-speed PCB design.
2,548
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RF Impedance Matching Network Phase differences/shifts
If there is a coax transmission line with the EM field propagating in the TEM mode and I measure the voltage signal off the inner conductor to an independent ground not part of the RF circuit and ...
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28 views
Using a single MOSFET as an RF switch
I'm assembling a receiver kit from QRP labs. It is an inexpensive kit designed to cover HF. This kit has a BS170 at the input which I assume is intended to disconnect the receiver when the transmitter ...
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2answers
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What is the purpose of this capacitor in the SA602A circuit and how do I choose its value?
I'm trying to use the SA602A mixer and I'm not sure what the capacitor between the emitter and the base does. I'm using this mixer because I've seen it being used in the Norcal40. However in the ...
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20 views
Find PCB Antenna impedance and matching circuit
I'm working on a project that uses NFC interface. I need to design two antennas: one for the RFID tag and another for the NFC initiator.
I decided to use the design proposed in the evaluation kits.
...
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58 views
Detecting an electrical connection without a complete circuit
Wired Fencing
In a regular (wired) fencing system (for sabre and foil,) contact is determined simply by applying a current to the weapon through a wire and forming a circuit between a conductive ...
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2answers
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Non-90deg mitered bends
Is there an approximate equation giving the optimal miter for a non-90degree mitered bend? In particular, I'm trying to determine the correct miter for a 45degree bend. There are a number of resources ...
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29 views
Calibrate for an inaccurate 50 ohm load in a DIY Vector Network Analyser (VNA) based on a VSWR RF bridge
I have built a "DIY VNA" using a frequency generator, an SDR receiver, a RF Reflection Bridge and a 50 ohm load. This is used to measure "VSWR values" of antennas to see what frequencies they are ...
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63 views
Key fob receiver reverse engineering: IC identification
I'm doing reverse engineering on a hardware of an equipment, this equipment is able to identify the presence of a RF signal from a key fob.
Unfortunately, it was not possible to identify the ...
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32 views
RFID reader array using row/column RF switches (multiplexers)
I need an 8x8 grid of RFID readers arranged on an 8"x8" board. The RFID tags will be placed only millimeters above each antenna.
I was wondering if I could use one 1:8 RF switch (e.g. pSemi PE426482) ...
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2answers
64 views
RF Power Amplifier outputting insufficient power
I'm using an SE5004L 5GHz power amplifier to generate a transmission signal in a radar application. I've designed the output power of this amplifier to be about 26dBm. Unfortunately, the measured ...
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26 views
Signal to Noise Ratio and return loss
If I measure a receiver NF as well as its input return loss. Then SNR = signal power/ noise power over the whole signal BW. Note that NF is used here
Now a bad return loss implies that part of the ...
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30 views
Receiver input return loss , Noise Figure and SNR
Suppose I measure a receiver NF and also its input return loss.
The known approach to calculate input referred SNR ,say at sensitivity level is:
signal power at sensitivity level/ noise power over ...
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1answer
90 views
DRM'd hand sanitizer dispenser
We have a newborn and rely on hand sanitizer when changing diapers, and we ran out at an inopportune moment in history. By some stroke of luck, I managed to snag one of those "industrial" touchless ...
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1answer
44 views
Soldered wire or test connector for VNA measurement?
I am designing a PCB for a IoT device, which will have an antenna inside a space-constrained plastic enclosure with metal screws. I know that I will have to tune the frequency response of the antenna ...
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2answers
42 views
LF RFID signal jammers
I am currently researching into the security of RFID based access control in relation with jammers. For an experiment, I am trying to build a device that can jam 125 kHz RFID cards from like a meter ...
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2answers
36 views
Waveguide excitation through coaxial antenna
let's consider a waveguide excited with a coaxial cable antenna:
You may see that this structure is sized with a distance between the antenna and the plate equal to \$\lambda/4\$. My professor has ...
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28 views
RF Communication Fresnel Zone Issues
I'm working on an two systems, each with the following connections:
433 Mhz
900 Mhz
5.8 Ghz
All links are omni-directional and vertically polarized. Only 1 set of (3) links are active at a given ...
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1answer
58 views
What does a discrete component mixer look like?
I'd like to make a poor man's mixer from scratch. Something that can down convert 7MHz to 100KHz. What would the circuit look like using only BJT/FETS or diodes?
EDIT:I found some some using diodes. ...
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2answers
37 views
One port Vector Network Analyzer (VNA) Calibration without the given standard Calibration Kit
I am trying to do a one port VNA calibration for measuring filters at the GHz band. The VNA that I am using is Keysight E5063A. However, I am running into some conceptual as well as some practical ...
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1answer
38 views
Bluetooth power standard values
Let´s say I have a device with a bluetooth (BLE) 5.1 radio and I would like to know when, using a mobile phone, the power received from the device is good enough to stablish a reliable communication ...
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2answers
59 views
LC Filter / Matching - Why does this cap help?
this is my first question on the site, so please let me know if there's something I can do to write it more helpfully.
The Problem: I'm building a small radio. At the output of my mixer, I need to ...
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2answers
38 views
Usage of non-linear phase filters in RF receivers
I'm in the process of designing the analog front end for a RF receiver. The system will use BPSK modulation. I was wondering what effect non-linear phase filters (such as Chebyshev and Butterworth) ...
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Which kind of IC is it [duplicate]
Does anyone know which kind of IC is it? Is it used to determine whether the key is open or not. Becuse the side of key high voltage RF is exist, transformer is used as a isolator.
When the key is ...
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Part number of the unknown IC [duplicate]
Does anyone know the part number of this IC or which kind of IC is it? When the key is open, voltage of pin 7 is sinusoidal 50KHz and 400mv peak to peak and the output voltage (pin 4) is Zero volt. ...
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29 views
Problem with received GPS data
I am using an mtk3333 to read gps coords. I set nmea messages to only output gll data. The problem is that I am receiving the GLL packets but in this format:
$GNGLL,,,,,004912.869,V,N*6D
GLL packets ...
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1answer
44 views
Why don't these even/odd mode transmission line results math up?
In Pozar's Microwave Engineering, he analyzes the Wilkinson power divider using even-odd mode analysis. His results match the expected values and power conservation is satisfied. Similar derivations ...
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Kind of Ic or its part number [closed]
Does anyone know the part number of this ic or which kind of ic is it?
When the key is open voltage of pin 7 is sinusoidal 50KHz and 400mv peak to peak. And Output is (pin 4) is Zero.
When the key is ...
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1answer
24 views
Attenuation and Insertion Loss for a 2 port network
in my university lectures the insertion loss and the attenuation of a 2 port network have been defined in the following way (and I have an extremely basic question about them):
the Lnsertion Loss L ...
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1answer
72 views
Why use convolution for pulse compression in radar instead of correlation?
I have not understood the way to process pulse compression in radar signal processing. I think it's correct to use correlation for pulse compression, but I saw many materials about pulse compression. ...
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1answer
58 views
Query regarding RF [closed]
I have few questions about RF.
In the RF they will mention the term "transmitting power." What does it exactly mean, if the transmitting power is more then what will happen?
If they mention a ...
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18 views
How close can I put my GPS/nb-IoT antennas to my nrf9160 SIP?
I'm designing an asset tracking product that needs to fit in a very compact space. I can just about squeeze the nrf9160 and my two antennas (un-amplified PulseLarsen W3011 for GPS, Taoglas NCP5820 for ...
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1answer
39 views
Dynamically setting address of HT12E with Raspberry Pi
I have a project where I need to send a wireless signal to one of several receivers to turn on an LED.
One transmitter, several (many) receivers, each with an LED.
The receivers need to have low ...
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29 views
Loop Filter in an ADPLL
I am implementing an ADPLL in an FPGA with VHDL, and I am encountering a problem in correctly implementing the loop filter. The code that I currently have for the loop filter is the following :
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1answer
138 views
How do I calculate a PCB antenna trace width?
I'm totally stuck here trying to find a single source that describes how to determine a PCB antenna trace width. I understand how to determine the length based on the targeted wavelength, but the ...
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3answers
45 views
Frequency demodulation with a spectrum analyzer
In my university lectures I have generated an FM signal (for instance with carrier frequency of 2GHz, frequency deviation equal to 100kHz, and modulating frequency equal to 100kHz.)
In order to ...
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0answers
53 views
Why circuit from antenna datasheet is like this?
I'm designing circuit with nRF52810 BLE SoC and I have decided to go with ceramic chip antenna because it seems easier than designing printed antenna. The problem is that I'm just a 1st year student ...
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1answer
50 views
What does the 25 Ω termination resistor do in a 0/180-degree hybrid power splitter?
The circuit in the picture is a 3dB power splitter using a 0/180-degree hybrid transformer/balun.
I see the impedance ratio of the transformer is \$ (14/10) ^2 \approx 2 \$, thus the equivalent ...
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9 views
Bluetooth Advertisements with multiple PHYs?
One thing I am confused about on Bluetooth 5. There are several different PHYs available on Bluetooth 5. My question is, can devices listen and/or send advertisements with multiple PHYs? What is ...
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Can I replace this filtering network with a saw filter chip?
The above image is the Application Circuit from the A7105 radio transciever chip's data sheet.
I think I am beginning to understand the purpose of most of these components.
I suspect that the ...
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68 views
Making my own coaxial hardline
I need about 50mm of coax hardline. I don't have any at home, but I do have a lathe, some copper, and some teflon stock.
Can I make my own coax hardline on the lathe? According to my calculations, ...
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1answer
54 views
How to identify remote keyless entry (RKE) frequency?
I need to design a system able to identify which frequency is being used by remote keyless entry (RKE). I found that the wireless carrier frequency can be 315MHz in the US/Japan and 433.92MHz (ISM ...
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0answers
41 views
Prevent Reception from an Extended Distance (Beyond Design)
I have a magnetic field that is being induced onto a power line by a transmitter, which is following the length of the power line to the receiver. The receiver communicates via a loosely coupled coil ...
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46 views
Effects of wood on UHF transmission
I have set up the following scenario in gprmax. From the results obtained using the software, I realized that when I increased the wood thickness the power received at the receiver increases instead ...
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2answers
62 views
What is the maximum frequency to use diodes for distortion?
What is the maximum frequency to use rectifier, Schottky or Zener diodes for cut off sin wave to square wave?
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Compensation for dielectric losses in a coil?
Recently I built a helical resonator. It took me a good while to adjust it since I had to trim my coils much shorter than calculated. The calculation said 7.2 turns but it ended up being more like 6.5 ...
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2answers
83 views
Avoiding ground loops with multiple coax cables
I have to connect two devices with multiple coax cables each carring a signal that has frequency components ranging from DC to a few GHz. I don't know how to avoid ground loops with this type of ...
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1answer
69 views
How much RF power can a microstrip line handle?
Transmission lines on printed circuit boards must be impedance controlled lines since we want to transmit the full power and avoid the reflections.
Microstrip lines have three parameters that we can ...
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3answers
100 views
Why is a horizontal rod a full wavelength oriented radially to a broadcast antenna not the best receiving antenna
I have always struggled to get a good physical understanding of Electromagnetic waves. I've done the whole Maxwell's equation approach, wrote boundary element solver tool but cannot rationalize that ...
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1answer
60 views
What is the purpose of these components in an LC Balun?
I'm trying to understand an antenna impedance matching / balun network that I came across in the receiving signal path in the schematics for the STEVAL-FKI868V2 S2-LP Evaluation Board, shown in the ...
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Butler Matrix simulation in Sonnet software
I am trying to replicate a 4 X 4 butler matrix using Sonnet
Here is the sonnet design file : butler_matrix.son
With conformal meshing (metal fill type) and course meshing, it still requires 14 GB of ...
